Thermoplastic polyoxymethylene molding resins

ABSTRACT

An improved thermoplastic molding resin comprising intimately mixed polyoxymethylene polymers and reinforcing agents in the presence of a thermoplastic phenoxy resin.

United States Patent [191 Freed Aug. 26, 1975 THERMOPLASTICPOLYOXYMETHYLENE MOLDING RESlNS [75] Inventor: William T. Freed,Madison, NJ.

{52] US. Cl H 260/37 AL; 260/823 [51] Int. Cl. C08L 7l/02 [58] Field ofSearch 260/37 AL, 830 R. 823

[56] References Cited UNITED STATES PATENTS 3.2 l 3.l58 10/1965Sakakibara et a]. i. 260/830 R 3/[972 ll/l973 Nagamatsu et al 260/37 ALBraunstein 260/37 AL Primary Examiner-Lewis T. Jacobs Attorney, Agent,or FirmThomas J. Morgan; Linn l. Grim; Marvin Bresslcr 5 7 ABSTRACT Animproved thermoplastic molding resin comprising intimately mixedpolyoxymethylene polymers and reinforcing agents in the presence of athermoplastic phenoxy resin.

10 Claims, No Drawings THERMOPLASTIC POLYOXYMETHYLENE MOLDING RESINS Thepresent invention relates to the products and process for preparingimproved thermoplastic molding resins. More specifically, this inventiondescribes im' proved reinforced polyoxymethylene polymers.

Reinforced polyoxymethylene polymers as described in US. Pat. No.3,455,867 provide increased strength properties in molded articles,however chemical coupling agents are required to provide theseimprovements. Thus, a chemical reaction is required and it is difficultto control this insitu reaction to obtain reproducible product. Usuallythe molded reinforced polyoxymethylene polymers have difficulties inproviding smooth surface properties since the reinforcing agents tend toextend through the polymer surface. Even with these slight problemsreinforced polyoxymethylene polymers are outstanding thermoplasticmolding resins.

It has now been discovered that improved thermoplastic reinforcedpolyoxymethylene polymers are provided by the incorporation of smallamounts of specific high molecular weight phenoxy resins in these compositions. The compositions of this invention not only provide improvedphysical properties but provide improved surface effects of the moldedarticles.

Oxymethylcne polymers having recurring CH O units, have been known formany years. They may be prepared by the polymerization of anhydrousformaldehyde or by the polymerization of trioxane, which is a cyclictrimer of formaldehyde.

Thus, the oxymethylene copolymer used in carrying this invention intoeffect may be a polymer having a structure comprising recurring unitsrepresented by the general formula wherein each R. and R is selectedfrom the group consisting of hydrogen, lower alkyl andhalogensubstituted lower alkyl radicals, and wherein n is an integerfrom zero to three, inclusive, and n being zero in from 85 to 99.9 molepercent of the recurring units. Each lower alkyl radical preferably hasfrom one to two carbon atoms, inclusive.

The oxymethylene copolymers produced from the preferred cyclic ethershave a structure composed substantially of oxymethylene and oxyethylencgroups in a ratio of from about 6 to l to about 1,000 to l.

The oxymethylene copolymers described briefly above are members of thebroader group of such copolymers that are useful in practicing thepresent invention and which have at least one chain containing recurringoxymethylene units interspersed with -OR groups in the main polymerchain. In such OR- groups, R represents a divalent radical containing atleast two carbon atoms linked directly to each other and positioned inthe polymer chain between the two valenccs with any substituents on saidradical being inert. that is. substitucnts that are free frominterfering functional groups and do not induce undesirable reactionsunder the conditions involved.

Among such copolymers that advantageously may be employed in practicingthis invention are oxymethylene copolymers containing from about 60 molepercent to 99.9 mole percent of recurring oxymethylene groups to from0.l mole percent to about 40 mole percent of OR groups. As indicatedhereinbefore, the most preferred copolymers are those having from aboutmole percent to 99.9 mole percent of recurring oxymethylene groups andfrom about 0.l to 15 mole percent of OR groups. In a preferredembodiment R may be, for example, an alkylene or substituted alkylenegroup containing at least two carbon atoms.

Also useful in carrying the instant invention into effect areoxymethylene copolymers having a structure comprising recurring unitsconsisting essentially of those represented by the general formulawherein n represents an integer from O to 5, inclusive, and representing0 (zero) in from 60 to 99.6 mole percent of the recurring units; and Rand R" represent inert substituents, that is, substituents which arefree from interfering functional groups and will not induce undesirablereactions. Thus, one advantageously may utilize oxymethylene copolymershaving a structure comprising oxymethylene and oxyethylene recurringunits wherein from 60 to 99.9 mole percent of the recurring units areoxymethylene units.

It has previously been indicated that especially pre ferred copolymersemployed in practicing the present invention are those containing intheir molecular structure oxyalkylcne units having adjacent carbon atomswhich are derived from cyclic ether having adjacent carbon atoms. Suchcopolymers may be prepared by copolymerizing trioxane or formaldehydewith a cyclic ether represented by the general formula wherein nrepresents an integer from zero to 4, inclusive, and R represents adivalent radical selected from the group consisting of (a) CH (b)CH O,and (c) any combination of CH and CH- O.

Examples of specific cyclic ethers that may be used in preparingcopolymers of this invention include cyclic ethers, l,3,5-trioxepane,l,3-dioxepane, betapropiolactonc, gamma-butyrolactone, neopentyl formal,pentaerythritol diformal, paraldehyde, and butadiene monoxide. Inaddition, glycols including, for example, ethylene glycol, diethyleneglycol, l,3butylene glycol, propylene glycol and the like, may beemployed instead of the cyclic ethers, acetals and esters justmentioned.

Although formaldehyde is a desirable source of the oxymethylene moiety(i.e., R 0 wherein R-, represents methylene or substituted methylene),it will be under stood, of course, by those skilled in the art thatinstead of formaldehyde, other sources of the oxymethylene moiety may beused; e.g., paraformaldehyde, trioxane, acetaldchyde, propionaldehyde,and the like. One may also employ cyclic acetals, e.g.,1,3,5-trioxepane, in that of epoxy resins. They are, however, a separateand lieu of both the cyclic ether and formaldehyde. unique resin class.differing from epoxies in several im- As used in the specification andclaims, the term portant chara teri ti oxymethylene polymers denoteshomopolymcrs and I :opolymcrs (including terpolymers, etc.) having at 5ihcnoxy resins are tough and ductile thermoplasleast 60 percentrecurring oxymethylene units, and furtics' Their average molecularweight ranges from ther includes substituted oxymethylene polymers,15,000 to 75900 preferably from 20900 to 50,000 wherein the substituentsare inert, i.e., do not particicompared with 340 to 11000 forconventional P' pate in undesirable Side reactions oxies which crosslinkon polymerization.

Also, as used in the specification and claims of this 2. Phenoxy resinsdo not have terminal highly reacapplication, the term copolymcn meanspolymers obtive epoxy groups and are thermally stable materitained bythe copolymerization of two or more differals with a long Shelf |ife Emmonomers n P y contilihihg in their 3. The phenoxy resins can be usedwithout further lecular Structure NO or more different monomer hemicalconvcrsi0n require no catalysts units), and includes terpolymers,tetrapolymers and i5 curing agents or hardeners to b f l products highmulticomponent polymers. The term polymer" while epoxy resins requirecatalysts, curing agents (unless it is clear from the context that thehomopolyor hardener to be u eful, mer or a eopolymer is intended)includes within its The phenoxy resins utilized herein can be charactermeaning both homopolymers and eopolymers. ized by a repeating structure:

I H H CH, H H H H H .1 1.. H H H H The oxymethylene polymers that aremodified acand having an average molecular weight range from cording tothis invention are thermoplastic materials about 15,000 to 75,000. As isobvious, the terminal having a molecular weight of at least 5,000, amelting structure is completed with hydrogen atoms or some point of atleast 100C. and an inherent viscosity of at suitable end capping groups.least 0.6 (measured at 60C. in a 0.1 weight percent so- Thethermoplastic phenoxy resin can be added to the lution in p-chlorophenolcontaining 2 weight percent of r inf ce xym hy ne r in n a m r f y lalpha-pinene), preferably they have a molecular weight y ihcotpotatihg tp y teih Ohto the reinforcing of at least 10,000, a melting point of atleast 150C. and agent Prior to its intimate biendmg with the y yaninherent viscosity of at least 1.0 (measured at 60C. iene resins (2) ySih'iuitahtiousiy intimately mixing in a 0.1 weight percent solution inp-chlorophenol conwith the reiflfol'ciflg ge t and the oxymethyleneresins taming 2 waight percent of a|pha pinene) and (3) by blending withthe polymer and intimately blending with the reinforcing agents. Othermixing The oxymethylene polymer component used in this 40 techniques canb used ihVehtiQh y be, if desired, 0itymethyiehc P y The amountofphenoxy resin incorporated can range that have been preliminarilystabilized to a substantial f about Q to about 8 i h percent f r blydegree- Such Stabiiizihg technique y take the fOrm from about 0.5 toabout 3 weight percent of the total of stabilization by degradation ofthe molecular ends of [hermgplastic oxymethylene ldi i the polymer chainto a point where a relatively stable The reinforcing agents as utilizedherein which procarbon-to-carbon linkage exists at each end. Forexamvide increased strength to the molded product can be ple, suchdegradation may be effected by hydrolysis as intimately mixed by eitherdry blending or melt blend disclosed in Canadian Pat. No. 725,734 issuedto Frank ing, blended in extruders, heated rolls or other types of M.Berardinelli on Jan. 11, 1966, assigned to the same mixers. If desired,the reinforcing agents can be assignee as the present invention, and bythis crossblended with the monomers in the polymerization reacrefercnceis made a part of the disclosure of the instant tion 35 g as thePolymerization reaction is not application fected. The type of fillerswhich can be used include among others, glass fibers (chopped orcontinuous rovwhiie P to as much 35 Percent Of the Polymeric ings),asbestos fibers, cellulosic fibers, synthetic fibers, Qhflins 0f theoxymethylcnc p y y Contain including graphite fibers. acicular calciummetasilicate minal hydroxymethyl or hydroxyalkyl groups (i.e.. hyand thelike. The amount of reinforcing agent can drOXy bonded to methylene 01'high r lkylene groups) range from about 2 to about weight percent,preferthe oxymethylene polymers may also contain active ably 5 to 60weight percent based on the total molding hydrogen-containing groupsbonded to or adjacent cocomposition. polymeric units derived from thecomonomers dc- 60 The following examples will serve to illustrate theinscribed above and in the aforementioned article by vention withoutlimiting the same. EXAMPLES The phenoxy resins utilized herein are highmolecu- Polyoxymethylenc copolymers (ethylene oxide) havlar weightthermoplastic resins which are produced ing number average molecularweight of 35,000 was from 3.2- i -hydroxyphenyl) pr pane andepichlotumble blended with glass fibers (V; inch length) and rohydrinaccording to the procedure as described in then extrusion blended byforce feeding through a l U.S. Pat. No. 3,356,646 issued Dec. 5, 1967.The basic inch single screw extruder with a strand die. The ternchemical structure of the phenoxy resins is similar to peraturcs of theextruder and die were set at 400F.,

400F. 420F. (from barrel to die). The strands were chopped in a rotarychopper to Va inch lengths. In the use of additives, phenoxy resin, freeof epoxide groups, prepared from 2,2-bis( 4-hydroxyphenyl) propane andepichlorohydrin having a number average molecular weight in the rangefrom 27.000 to 29,000 can be added in the tumble blender or in theextrusion blender. The diepoxide of reaction product of 2,2-

weight of at least 10,000 and a melting point of at least 150C;reinforcing agents intimately mixed with said polymer; and from about 0.l to about 8 weight percent of a thermoplastic phenoxy resin having arepeating structurel H H H H bis(4 hydroxyphenyl) propane and.epichlorohydrin CH H H H having a number average molecular weight in therange 10 O (i- O (i- (i from 8,000 to 12.000 can be added in theidentical 1 places as the phenoxy resin. Reference to the diepoxide CH3H H H is hereinafter described as epoxy. H H H H The various materialswere molded into tensile test bars under the following conditions: [5

and an average molecular weight range from about Processing Temperature400: ISOOO to about s ci iv si j 53%; 2. The product of claim 1 whereinthe amount of re- Tmfll Cycle Time 55 inforcing agent ranges from about5 to about 60 weight percent of the total thermoplastic molding resin.

The results in Table l utilize weight percent glass fibers (143 inchlength) intimately mixed with polyoxy 3. The product of claim 2 whereinthe reinforcing methylene copolymer (ethylene oxide) in the presenceagents are glass fibcrs' of various amounts of additives such as phenoxyresin 25 4, Th rodu t of laim 2 wherein the reinforcing and p y agent isacicular calcium metasilicatev TABLE I Comparative Properties of 25%Glass Reinforced Polyoxymethylene Copolymer with Phenoxy Resin and EpoxyAdditives Amount of Additix e I\\'t. 'w' of total composition) None0.5V: in 1.5% 27/ Type of Additive None Phenox Epoxy Phenoxy EpoxyPhcnoxy Epoxy Phenoxy Epoxy Tensile Strength. psi 10,050 l6,520 l5,filtll7,2()5 l4,74(l l6.445 l4,452 l7,l()(l 13.930 Elongation /1 1.5 2.4 2.4l.9 2.2 2.5 2.9 2.3 2.3 knergy to Break in lh 23.9 78.2 65.0 85.8 56.375.l 56,] 81.0 48.0 l-lewral Strength. psi 29l92 2!.362 23,964 0,3 522,911 20,337 23,547 lhfltil Flexura! Modulus ll)". psi 0.984 0.9430.995 0.9. (1.988 0.957 0.982 0.927 Notched l/od, ft/lhs notch 1.02 1.291.19 L46 I. ll L3H l.l5 1.43 H); A lh. Gardner Impact in lh 2.12 2.252.25 3.]2 2 12 2.87 2.25 2.62 L75 The comparative results of Table 1indicate that the presence of phenoxy resin and epoxy resin providevastly improved physical properties over the control containing noadditives. The presence of phenoxy resin, however, provides significantimprovements over the epoxy resin in tensile strength. flexuralstrength, impact, among other properties. This is indeed surprisingconsidering that the phenoxy resin does not appear to have reactivegroups such as the epoxy resins do. It is further surprising that thephenoxy resin additive, known as an adhesive, is compatible with thereinforced polyoxymethylene copolymer and providing outstandingly smoothsurface effects when compared with the control (no additive) sample.

Similar outstanding results as above with the phenoxy resin are obtainedwhen the phenoxy resin is incorpo rated onto the reinforcing agent priorto the intimate mixing of the reinforcing agent and the polyoxymethylenehomopolymer or copolymer.

What is claimed is:

1. An improved thermoplastic molding resin comprising a normally solidoxymethylene polymer having an inherent viscosity of at least 1.0(measured at 60C. in a 0.1 weight percent solution in p-chlorophenol containing 2 weight percent of alpha-pinene), a molecular 5. The product ofclaim 2 wherein the oxymethylcne polymer is a capped homopolymer.

6. The product of claim 2 wherein said oxymethylene polymer is anoxymethylene copolymer comprising from about mole percent to 99.9 molepercent recurring OCH groups.

7. The product of claim 2 wherein the amount of phenoxy resin rangesfrom about 0.5 to 3 weight percent of the total thermoplastic moldingresin and said phenoxy resin having an average molecular weight rangingfrom about 20,000 to about 50,000.

8. A process for producing an improved thermoplastic molding resinwherein a normally solid oxymethylene polymer having an inherentviscosity of at least [.0 (measured at 60C. in a 0.l weight percentsolution in p-chlorophenol containing 2 weight percent of alphapinenc),a molecular weight of at least l0,000, and a melting point of at leastC, is intimately mixed with about 5 to 60 weight percent of the totalmolding resin of a reinforcing agent in the presence of from about 0.1to about 8 weight percent of the total molding resin ofa thermoplasticphenoxy resin having a repeating structure and an average molecularweight range from about 15.000 to about 75,000.

1. AN IMPROVED THERMOPLASTIC MOLDING RESIN COMPRISING A NORMALLY SOLIDOXYMETHYLENE POLYMER HAVING ANINHERENT VISCOSITY OF AT LEAST 1.0(MEASURED AT 60*C, IN A 0.1 WEIGHT PERCENT SOLUTION IN P-CHLOROPHENOLCONTAINING 2 WEIGHT PERCENT OF ALPHA-PINENE), A MOLECULAR WEIGHT OF ATLEAST 10,000 AND A MELTING POINT OF AT LEAST 150*C., REINFORCING AGENTSINTIMATELY MIXED WITH SAID POLYMER, AND FROM ABOUT 0.1 TO ABOUT 8 WEIGHTPERCENT OF A THERMOPLASTIC PHENOXY RESIN HAVING A REPEATING STRUCTURE:2. The product of claim 1 wherein the amount of reinforcing agent rangesfrom about 5 to about 60 weight percent of the total thermoplasticmolding resin.
 3. The product of claim 2 wherein the reinforcing agentsare glass fibers.
 4. The product of claim 2 wherein the reinforcingagent is acicular calcium metasilicate.
 5. The product of claim 2wherein the oxymethylene polymer is a capped homopolymer.
 6. The productof claim 2 wherein said oxymethylene polymer is an oxymethylenecopolymer comprising from about 85 mole percent to 99.9 mole percentrecurring -OCH2- groups.
 7. The product of claim 2 wherein the amount ofphenoxy resin ranges from about 0.5 to 3 weight percent of the totalthermoplastic molding resin and said phenoxy resin having an averagemolecular weight ranging from about 20,000 to about 50,
 000. 8. Aprocess for producing an improved thermoplastic molding resin wherein anormally solid oxymethylene polymer having an inherent viscosity of atleast 1.0 (measured at 60*C. in a 0.1 weight percent solution inp-chlorophenol containing 2 weight percent of alpha-pinene), a molecularweight of at least 10,000, and a melting point of at least 150*C., isintimately mixed with about 5 to 60 weight percent of the total moldingresin of a reinforcing agent in the presence of from about 0.1 to about8 weight percent of the total molding resin of a thermoplastic phenoxyresin having a repeating structure
 9. The process of claim 8 wherein thereinforcing agent is glass fibers.
 10. The process of claim 9 whereinthe thermoplastic phenoxy resin is incorporated on the reinforcing agentand then intimately mixed with the polyoxymethylene polymer.